50 Fun Facts About Ceres

Where in the Solar System is the dwarf planet Ceres?

It is the only dwarf planet inside Neptune's orbit and the largest object in the belt.

Who discovered Ceres, and on what date?

A Catholic priest in Palermo, he found it on the first night of the 19th century while checking a star catalogue.

Piazzi found Ceres from an observatory on which island?

Ceres, the goddess of grain, had her oldest temple in Sicily, which suited the name.

What did Piazzi first think his moving object was?

Its slow, steady motion soon made him suspect something better than a comet.

Which 24-year-old mathematician invented a new orbit method to recover Ceres after it was lost in the Sun's glare?

Von Zach and Olbers found Ceres near his predicted spot on the last day of 1801.

Ceres seemed to fill the gap predicted by which formula, which had already 'predicted' Uranus's distance?

The rule called for a planet at about 2.8 AU, and Ceres orbits at almost exactly that distance.

What full name did Piazzi propose for his discovery?

The second part honoured King Ferdinand III of Sicily; other nations refused to use it.

Ceres is named after the Roman goddess of what?

The word cereal comes from her name; the Greeks called her Demeter.

Which everyday word derives from the goddess Ceres?

Her son Liber, later Bacchus, represented wine and good living.

What is the old astronomical symbol of Ceres, still used in astrology?

It looks like the Venus symbol with a break in the circle; von Zach and Bode both suggested it in 1802.

What word did William Herschel coin in 1802 for Ceres and its newly found neighbour Pallas?

It means 'star-like', because even good telescopes could not show them as discs.

For roughly how long was Ceres listed as a planet in astronomy books and tables?

Pallas, Juno and Vesta shared the honour until asteroids became too numerous.

What number does Ceres carry in the minor planet numbering system?

The numbering originally began with 5 Astraea as number 1; Ceres was slotted in as number 1 in 1867.

Ceres was reclassified as a dwarf planet in the same 2006 IAU decision that demoted which body?

It is the only dwarf planet in the inner Solar System and the largest without a moon.

What is Ceres's mean diameter, as measured by Dawn?

That is roughly a quarter the diameter of the Moon.

How does Ceres's diameter compare with the Moon's?

Its mass is only about 1/78 of the Moon's, though.

Roughly what fraction of the whole belt's total mass is Ceres?

It has three and a half times the mass of Vesta, the next biggest.

How long does Ceres take to orbit the Sun?

It sits near the middle of the asteroid belt at about 2.8 AU.

How long is a day on Ceres?

The small equatorial crater Kait marks its prime meridian.

Ceres is thought to be roughly what proportion water by volume?

Earth, by comparison, is about 0.1% water by volume; Ceres has more water than any inner Solar System body except Earth.

Which spacecraft became the first to orbit Ceres, arriving in March 2015?

It had already spent 13 months orbiting Vesta, making it the first craft to orbit two extraterrestrial bodies.

Dawn holds which record among spacecraft?

It was also the first to orbit a dwarf planet, four months before New Horizons reached Pluto.

What kind of propulsion let Dawn leave Vesta and travel on to Ceres?

The gentle but efficient drive made the two-stop tour possible.

Ceres's famous bright spots lie mostly in the middle of which 80-km crater?

The central spot is Cerealia Facula and the cluster to its east is Vinalia Faculae.

What are the bright spots on Ceres made of?

Sodium carbonate mostly, with ammonium salts, crystallised from brine that seeped up from below.

What did NASA confirm about Ceres in August 2020?

The brine wells up in hundreds of places, producing the bright spots.

What is Ahuna Mons, the one prominent mountain on Ceres?

With few craters it is at most 240 million years old, and it sits roughly opposite the big Kerwan basin.

What is the largest confirmed crater on Ceres?

At 284 km it is far smaller than models predicted, because the icy crust slowly relaxes and flattens old scars.

Organic compounds were detected on Ceres in which crater?

Its near-surface is about 20% carbon by mass, five times richer than carbonaceous meteorites.

What did Dawn confirm in 2017 that Ceres has, at least intermittently?

The Herschel Space Observatory had spotted water vapour plumes in 2014.

How did the Dawn mission end in November 2018?

It was left in a stable orbit to avoid contaminating a possibly habitable body.

Ceres has been described as one of only three surviving what in the inner Solar System?

Pallas and Vesta are the other two; the rest merged into planets or were shattered.

How many natural moons does Ceres have?

It is the largest dwarf planet without a moon, perhaps because of its differentiated interior.

At its very brightest, can Ceres be seen with the naked eye?

It peaks at magnitude 6.7 at a favourable opposition; binoculars show it easily.

Ceres has been classed in which spectral group of asteroids, dark and carbon-rich?

Its clay minerals also earn it a G-type label, similar to carbonaceous chondrite meteorites.

The chemistry of Ceres suggests it may have formed where?

Its ultra-carbon-rich, water-altered material fits a cold birthplace before it migrated inward.

Ceres has more of what than any other body in the inner Solar System except Earth?

Its subsurface brine pockets could, in principle, harbour microbes.

Ceres's axial tilt of only 4 degrees means what at its poles?

Just as on the Moon and Mercury, cold traps there slowly collect water molecules.

Ceres orbits at about 2.8 AU. What was significant about that number in 1801?

Bode was convinced he had found his 'missing planet' between Mars and Jupiter.

Which German astronomer called the unconfirmed Ceres 'Juno', while von Zach called it Hera?

Piazzi objected, and once the object was recovered his own name stuck.

Who introduced the system of numbering asteroids in order of discovery, in 1852?

He found the old habit of giving each one a planetary symbol far too cumbersome.

How many boulders larger than 105 m across did Dawn count on Ceres's surface?

They cluster in and around craters, though not every crater has them.

An ESA team proposed which follow-up mission concept in 2020 to bring back samples of the bright spots?

It would return the bright carbonate salts and dark organics to Earth.

What did Hubble ultraviolet images in 1995 reveal on Ceres, nicknamed in the discoverer's honour?

Little else was known of the surface until Dawn arrived twenty years later.

Which other large body of the belt can regularly match Ceres for naked-eye brightness?

Pallas and Iris only manage it when at opposition and near perihelion together.

The goddess Ceres was originally the central deity of which Roman cult grouping?

She was later paired with her daughter Proserpina in what Romans called 'the Greek rites of Ceres'.

How long did the Cerealia, the goddess Ceres's April festival, last?

It included the popular Ludi Ceriales, or Ceres's games, and opened with a horse race in the Circus Maximus.

After the Cerealia horse race, which animals were loosed in the Circus with blazing tails?

The rite may have been meant to cleanse the crops of disease and vermin or add warmth to their growth.

Ceres is the only Roman agricultural deity listed among which group of twelve major gods?

The group was Rome's equivalent to the Twelve Olympians.

According to Cicero, Ceres was the mother of which two deities?

Varro's more complex theology instead grouped her functionally with Tellus, Terra and Venus.