Dwarf Planet 136108 Haumea approaches opposition.

The Dwarf Planet 136108 Haumea will reach opposition (i.e. be directly opposite the Sun seen from Earth) at 8.47 am GMT on Thursday 23 April 2026. This means that it will both be at its closest to the Earth this year, about 42.1 AU (42.1 times the average distance between the Earth and the Sun, or about 6 298 255 000 km), and completely illuminated by the Sun. While it is not visible to the naked eye observer, the planets have phases just like those of the Moon; being further from the Sun than the Earth, 136108 Haumea is 'full' when directly opposite the Sun. 

The orbit and position of 136108 Haumea and the planets of the Solar System at 9.00 am on Thursday 23 April 2026. JPL Small Body Database Browser.

At opposition, the Dwarf Planet will be in the constellation of Bootes and at its highest point in the sky at about midnight local time from anywhere on Earth (this is because the rising and setting of objects in the sky is caused by the Earth's rotation, not the movement of the object). (Even at it's very brightest 136108 Haumea will only have a Magnitude of 17.3, making it almost impossible to see with any but the largest of Earth-based telescopes, and where resolvable it will only be possible to see it as a point of light indistinguishable from a faint star.

136108 Haumea orbits the Sun on an eccentric orbit tilted at an angle of 28.2° to the plane of the Solar System, which takes it from 34.4 AU from the Sun (34.4 times the average distance at which the Earth orbits the Sun) to 51.5 AU from the Sun (51.5 times the average distance at which the Earth orbits the Sun). With an average distance of 43.0 AU, 136108 Haumea completes one orbit around the Sun every 282 years. This means that the planet is almost stationary compared to the faster moving Earth, so that it reaches Opposition only one day later each year than the year before, and reaches Solar Conjunction (when it is directly on the opposite side of the Sun to the Earth), roughly six months later.

136108 Haumea was discovered on 28 December 2004 by a team led by Mike Brown of the Palomar Observatory in California, in images taken by them on 28 May 2004; on 27 July 2005 a team led by José Luis Ortiz Moreno and his team at the Instituto de Astrofísica de Andalucía reported that they had also discovered the Dwarf Planet, in images taken between 7 and 10 March 2003. With a diameter of 2100 km it is considered to be the third largest dwarf planet in the Solar System (after 134340 Pluto and 136199 Eris) as well as the eighteenth largest body in the Solar System, excluding the Sun (several moons, including our own, are larger).

Haumea has been calculated to be rotating once every 3.9 hours, far more rapidly than any other large body in the Solar System. Curiously for such a fast rotating body, it has not adopted a oblate spheroid (flattened sphere) shape, but is instead a triaxial ellipsoid (elongate flattened sphere, or flattened egg-shape). This implies that, although its surface is comprised of ice, it has a core of fairly dense rocky material. 

The Dwarf Planet Haumea is believed to rotate in just under 4 hours. This rapid rotation causes the Dwarf Planet to be elongated in appearance. Stephanie Hoover/Wikimedia Commons.

Although Haumea is only about a quarter the size of Pluto, it is thought to be large enough that it should have reached hydrostatic equilibrium (i.e. become approximately spherical due to its own gravity). The elongate shape of Haumea is at odds with this, something which, in combination with its high rotational rate, has been suggested as evidence of a major collision in Haumea's past. This has been supported by the discovery in 2017 of a ring surrounding the dwarf planet with a radius of about 2285 km. This is well within the Roche limit for Haumea (the distance below which a ring or other orbiting body should be disrupted by the parent body's gravity and either fall onto it or be ejected), suggesting that this is a temporary structure caused by a relatively recent event (although still potentially billions of years ago, given the weak gravitational forces involved).

136108 Haumea rotating within its ring system. Tom Ruen/Wikimedia Commons.

136108 has two small moons, both of which were discovered in 2005 by Darin Ragozzine and Michael Brown, at that time working at the W. M. Keck Observatory in Hawai'i. The larger of these, Hi'iaka, is roughly 370 km in diameter (although, like its parent body, it has been calculated to have an elongate, non-spherical shape) and orbits at a distance of 49 400 km, completing one orbit every 49.5 days. The smaller, Namaka, has been calculated to be about 150 km in diameter with an irregular shape, and to orbit at a distance of approximately 25 500 km.

Both the rings of 136108 Haumea and the larger moon, Hi'iaka, follow orbital paths 1-3° offset from the equator of the dwarf planet, and are thought to be products of the same collision. The smaller moon, Namaka, has an orbit offset by 69° from the equator of Haumea. This moon is thought to have been formed in the same collision, but to have had it's orbit perturbed significantly by tidal interactions with the larger moon.

Dwarf Planet Haumea and its satellites, imaged by the Hubble Space Telescope's WFC2 camera from 12 May 2008 and 19 May 2008. The brighter dot orbiting Haumea is the larger outer moon Hi'iaka while the fainter dot is the smaller inner moon Namaka. This animation of the moons' orbits spans 7 days and the orbital plane of Namaka is oriented vertically. Hubble Space Telescope/Michael Brown/Wikimedia Commons.

136108 Haumea is thought to be a member of a collisional family of Kuiper Belt objects; the only collisional family identified from this part of the Solar System. This family has been named the Haumea, or Haumean, Family in reference to its largest known member. Collisional families are groups of bodies which appear to have been created in a single collision event, and whose orbital trajectories can in theory all be traced back to a single point of origin, although this is not the case for the Haumea Family, which are thought to have had their orbital paths modified over time by interactions with the gravitational field of Neptune. 

As well as 136108 Haumea and its ring and moons, this family is thought to include the Kuiper Belt Objects (19308) 1996 TO66, (24835) 1995 SM55, (55636) 2002 TX300, (86047) 1999 OY3, (120178) 2003 OP32, (145453) 2005 RR43, (202421) 2005 UQ513, (308193) 2005 CB79, (315530) 2008 AP129, (386723) 2009 YE7, (416400) 2003 UZ117, (523645) 2010 VK201, (543454) 2014 HZ199, (612620) 2003 SQ317, (653589) 2014 QW441, (671467) 2014 LO28, and (673087) 2015 AJ281, as well, presumably, as other as yet undiscovered bodies.

The orbits of the bodies of the Haumea Collisional Family (not all are shown). Tom Ruen/Wikimedia Commons.

As well as having similar orbital properties, the bodies of the Haumea Family all share a similar high albedo (with the exception of (202421) 2005 UQ513), which suggests a surface largely covered by reflective water ice, rather than the darker, reddish, tholins (frozen organic compounds) which cover the surface of most Kuiper Belt objects. (202421) 2005 UQ513 has a lower albedo and a reddish spectrum, suggesting that it has an outer surface covered with tholins, but is included within the Haumea Family due to the similarity of its orbit.

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The furthest lunar apogee or 2025.

On Thursday 20 November 2025, at 2.49 am GMT, the Moon will be at its furthest point from the Earth in 2025, a distance of 406 692 km. The Moon orbits the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. Because this is an elongating and contracting elliptical orbit, rather than a change in the average distance between the Earth and the Moon, the most extreme Lunar Perigee and Apogee of each year typically happen in the same Lunar Month; this year the closest Lunar Perigee occurred at 10.30 pm GMT on Wednesday 5 November.

Diagram showing the relationship of the Lunar orbit and Lunar month. Southern Astronomical Delights.

Although this is the furthest point from the Earth that the Moon will reach in 2025, it is not exceptional. The Moon reached 406 710 km from the Earth on 29 March 1984, and will reach 406 705 on 1 December 2043. 

The Earth-Moon System to Scale, 650 km/pixel. John Walker/Fourmilab.

However, there is evidence that the Earth and Moon have been moving steadily apart since the formation of the Earth/Moon system, about 4.5 billion years ago. Studies of the shells of Rudists, a sort of Bivalve Mollusc which laid down layers of shell daily, have found that the Cretaceous year was 372 days long. Since the length of a year is unlikely to have changed without the Earth shifting profoundly on its orbit, the most plausible explanation for this is that the days were shorter. Since the length of the day is driven by the closeness of the Moon, that the Moon was significantly closer, with an average distance from the Earth of approximately 383 000 km in the Late Cretaceous (about 80 million years ago) compared to 384 400 km today. 

This fits with measurements that made by the  Lunar Laser Ranging experiments, which work byby bouncing lasers off a mirror left on the Moon. The first of these experiments was set up by NASA's Apollo Program, with additional mirrors being placed by the Soviet Lunokhod remote operated Moon vehicles, and the Indian Chandrayaan-3 mission. All of these experiments have shown that the Moon is moving away from us at an average of 38 mm per year.

Measuring the distance between the Earth and the Moon by bouncing a laser between the Earth and a mirror and the Moon. All distances are to scale, with the light moving in real time for the scale. James O'Donoghue/NASA/Solar System Scope/Wikimedia Commons.

This would seem to imply that the collision which is thought to have formed the Earth/Moon system would have occurred about 1.5 billion years ago, something for which there was no evidence. Studies of Mesoproterozoic Banded Ironstone formations in Australia have shown a 23.3 year variation in tidal cycles, which are also determined by the lunar distance. Today, these cycles follow an 18.6 year cycle, which suggests the average distance between the Earth and the Moon between about 1.5 and 2.0 billion years ago was approximately 332 000 km, suggesting that the rate at which the Moon is retreating from the Earth has increased over time.

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The closest Lunar Perigee of 2025.

At 10.30 pm GMT on Wednesday 5 November the Moon will be at its closest point to the Earth in 2025, at a distance of 356 832 km. This will fall nine hours and eleven minutes after the Full Moon, at 1.19 pm on the same day, making it particularly large in the sky. The Moon completes one orbit about the Earth every 27.5 days, and like most orbiting bodies, its orbit is not completely circular, but slightly elliptical, so that the distance between the two bodies varies by about 3% over the course of a month. This elliptical orbit is also not completely regular, it periodically elongates then returns to normal, making some perigees closer than others. These cycles mean that the Moon often reaches its furthest point from the Earth (apogee) of the year in the same lunar cycle, with the furthest Lunar Apogee of 2025 falling on 20 November.

Simplified diagram of the Moon's orbit. NASA.

Although this is the closest point to the Earth that the Moon has reached this year, it is not exceptional. The Moon reached 356 589 km from the Earth on 21 January 2023, and will reach 356 649 km from the Earth on 24 December 2026. The closest the Moon can come to the Earth is currently about 356 375 km, while its maximum distance is about 406 720 km.

The Earth-Moon System to Scale, 650 km/pixel. John Walker/Fourmilab.

However, there is evidence that the Earth and Moon have been moving steadily apart since the formation of the Earth/Moon system, about 4.5 billion years ago. Studies of the shells of Rudists, a sort of Bivalve Mollusc which laid down layers of shell daily, have found that the Cretaceous year was 372 days long. Since the length of a year is unlikely to have changed without the Earth shifting profoundly on its orbit, the most plausible explanation for this is that the days were shorter, and since the length of the day is driven by the closeness of the Moon, that the Moon was significantly closer, with an average distance from the Earth of approximately 383 000 km in the Late Cretaceous, about 80 million years ago, compared to 384 400 km today. This fits with measurements that made by bouncing lasers off a mirror left on the Moon by the Apollo Program astronauts, which have shown that the Moon is moving away from us at an average of 38 mm per year.

Measuring the distance between the Earth and the Moon by bouncing a laser between the Earth and a mirror and the Moon. All distances are to scale, with the light moving in real time for the scale. James O'Donoghue/NASA/Solar System Scope/Wikimedia Commons.

However, this would imply that the collision which is thought to have formed the Earth/Moon system would have occurred about 1.5 billion years ago, something for which there was no evidence. Studies of Mesoproterozoic Banded Ironstone formations in Australia have shown a 23.3 year variation in tidal cycles, which are also determined by the lunar distance. Today, these cycles follow an 18.6 year cycle, which suggests the average distance between the Earth and the Moon between about 1.5 and 2.0 billion years ago was approximately 332 000 km, suggesting that the rate at which the Moon is retreating from the Earth has increased over time.

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Total lunar eclipse to be visible from Asia, Africa, Australasia, and Eastern Europe.

A total Lunar Eclipse will occur on Sunday 7 September 2025, starting at 4.27 pm GMT. It will be visible across the entirety of Australia, Indonesia, Asia apart from areas of the Russian Far East, the Indian Ocean, and the eastern half of Africa. In Eastern Europe, much of Central and West Africa, New Zealand, Melanesia, and Micronesia, part of the eclipse will be visible, although in these areas the Moon will either rise part way through the eclipse, or set before it is complete in these areas.

Areas from which the 7 September 2025 Lunar Eclipse will be visible. Dominic Ford/In the Sky.

The Moon produces no light of its own, but 'shines' with reflected light from the Sun. Thus at Full Moon the Moon is on the opposite side of the Earth to the Sun, and its illuminated side is turned towards us, but at New Moon the Moon is between the Earth and the Sun, so that its illuminated side is turned away from us.

How the phases of the Moon are caused by the relative positions of the Earth, Sun and Moon. Karl Tate/Space.com.

Lunar eclipses occur when the Moon passes through the Earth's shadow. This can only happen at Full Moon (unlike Solar Eclipses, which happen only when the Moon passes between the Earth and the Sum, and therefore only occur at New Moon), but does not happen every Lunar Month as the Sun, Moon and Earth are not in a perfect, unwavering line, but rather both the Earth and the Moon wobble slightly as they orbit their parent bodies, rising above and sinking bellow the plane of the ecliptic (the plane upon which they would all be in line every month). 

Phases of the 7 September 2025. NASA Eclipse Website.

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James Webb Space Telescope discovers twenty ninth moon orbiting Uranus.

A team of scientists from the Southwest Research Institute in Boulder, Colorado, have discovered a new moon orbiting the planet Uranus in images taken by the James Webb Space Telescope, according to a press release issued by NASA on 19 August 2025. The team, headed by lead scientist Maryame El Moutamid, discovered the moon in a series of 40 second exposures of the planet taken on 2 February 2025.

The new moon has been given the provisional designation S/2025 U1 (indicating the first Satellite discovered orbiting Uranus in 2025). If the discovery is confirmed, it will be formally given a name, which in the case of moons of Uranus is chosen from characters in the plays of William Shakespear or Alexander Pope.

S/2025 U1 has an estimated diameter of 8-10 km, and orbits 56 250 km above the centre of Uranus (as a gas giant, Uranus does not have a 'surface'), between the moons Ophelia and Bianca. This makes it extremely faint, which combined with its proximity to the planet, appears to have hidden it from previous observations by Voyager 2 and the Hubble Space Telescope.

Discovery video of S/2025 U1 by the James Webb Space Telescope over the course of 10 frames. James Webb Space Telescope/NASA/European Space Agency/Canadian Space Agency/Wikimedia Commons.

S/2025 U1 is the first moon of Uranus discovered in two years, with the most recent discovery previously being S/2023 U1 (which has not yet been confirmed, and therefore still has a provisional designation) discovered in 2023 by American Astronomer Scott Sheppard using the 6.5-meter Magellan–Baade Telescope at Las Campanas Observatory in Chile. Prior to this, the moons Cupid, Mab, and Margaret were discovered in 2003 using the Hubble Space Telescope, while Francisco was discovered in the same year using the 4.0-meter Víctor M. Blanco Telescope at Cerro Tololo Observatory, again in Chile. In 2001 the moons Trinculo and Ferdinand were also discovered using the 4.0-meter Víctor M. Blanco Telescope. In 1999 the moon Perdita was discovered in photographs made by the Voyager 2 spacecraft during its flyby of Uranus in 1986. Also in 1999, the moons Stephano, Prospero, and Setebos were discovered using the Canada-France-Hawaii Telescope on Mauna Kea. In 1997 the moons Caliban and Sycorax were discovered using the 200-inch Hale Telescope at the Palomar Observatory in California. In 1986 the moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, and Belinda were discovered by the Voyager 2 Spacecraft during its flyby of Uranus, with Puck discovered the previous year as the spacecraft approached the planet.

Prior to this, the last moon of Uranus discovered had been Miranda, discovered in 1948 by Gerard Kuiper (after whom the Kuiper Belt is named), then working at McDonald Observatory in Texas. Almost a century before this the English astronomer William Lassell discovered the moons Ariel and Umbriel, using a 24 inch telescope he built himself and operated from a suburb of Liverpool. This first two moons of Uranus to be discovered (and its largest moons), Titania and Oberon, were discovered on 11 January 1787 by William Herschel, six years after he discovered the planet itself.

James Webb image showing S/2025 U1 and 13 of the 28 other known moons orbiting the planet Uranus. NASA/European Space Agency/Canadian Space Agency/Southwest Research Institute/Maryame El Moutamid/Matthew Hedman.

S/2025 U1 is the smallest moon of Uranus yet discovered, and appears to be the fourteenth member of a group of small moons orbiting inside the major moons of Uranus (Titania, Oberon, Arial, Umbriel, and Miranda) but outside the planets rings (the remaining moons are small bodies with eccentric and often retrograde orbits outside the major moons, which may be captured comets or asteroids). These small moons all have very circular orbits, which suggests that they formed in their current locations, hinting at a complex relationship with the particles of the rings.

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