Space News & Blog Articles

Red supergiant stars are explosions waiting to happen. They are in the last stage of their life, red and swollen as they fuse heavier elements in a last effort to keep from collapsing. But eventually, gravity will win and the red supergiant core will collapse, triggering a supernova. We know it will happen, but until recently, we didn’t know when.

The most famous red supergiant is Betelgeuse, the bright red star in the constellation Orion. It is about 550 light-years away and has a mass of about 18 Suns. It is the closest red supergiant to Earth, and when it eventually does explode it will briefly outshine the Moon. Of course, this has caused all manner of speculation about the star. Will it explode in our lifetime? Has it already exploded, and we’re just waiting for the supernova light to reach us? And all astronomers have been able to say is probably not, but we don’t really know. But a new study could give us an advance warning a few months before Betelgeuse does explode.

There are two general models for red supergiant supernovae. Both predict a red supergiant should dim significantly before exploding, on significantly different time scales. In the superwind model, a stellar wind is triggered by the ever-faster rate of fusion at a star’s end of life. The outer layer of the star is driven off by this wind over several decades, creating a circumstellar layer of cool gas that causes the star to appear very dim. The rapid outburst model, on the other hand, predicts a final period of less than a year, where more than a tenth of a solar mass can be cast off. This would cause the star to dim by a factor of 100 within the last few months of its life.

In this study, the team looked at all the red supergiant supernovae cases where the star was observed before its explosion. Most supernovae are only observed after the explosion, so between 1999 and 2017 there are only a dozen cases of good pre-supernova observations. But in all of those cases, the brightness of the stars remained fairly consistent in the years leading up to the supernovae. This would rule out the superwind model and suggests that a red supergiant should dim significantly before exploding. In the case of Betelguese, we have seen the star dim as it cast off a cloud of gas, but not to the level that indicates an eminent explosion.

Unfortunately, we don’t have enough red supergiant observations to have observed a rapid dimming before the bang, but that could change in the future as more long-term sky surveys come online. And who knows, given how well-studied Betelgeuse is, our red supergiant neighbor might be the first star to give us a supernova red alert.

DART’s results are in and they exceed all expectations. The Moon might just be a big chunk of the Earth that formed in just hours. Webb sees bizarre rings around a star, and SLS gets a new launch date… at night.

As always, if you prefer a video version of space news to accompany your morning coffee or other activities, here’s the latest episode of Space Bites. Delicious space news nuggets.

DART Exceeds NASA’s Expectations

When NASA directed its DART mission to slam into Asteroid Dimorphos, it hoped to shorten its orbital period around Asteroid Didymos. Seventy-three seconds was the bare minimum; 10 minutes would have been excellent. But when they ran the numbers, it looked like DART shortened the asteroid’s orbital time by 32 minutes. Before the impact, Dimorphos took 11 hours and 55 minutes to orbit; now, it’s 11 hours and 23 minutes. This provides a baseline that astronomers can use to calculate how difficult it’ll be to prevent a dangerous asteroid from hitting Earth.

More about DART success

How Did the Moon Form

Where did the Moon come from? The evidence is leaning towards the theory that a Mars-sized object crashed into the Earth billions of years ago, and the rubble collected together into the Moon. This goes partway to explaining the Moon, but there are a few outstanding mysteries, like how to explain the Moon’s orbit, which doesn’t orbit around the Earth’s equator. A new theory suggests that a single large asteroid strike blasted two huge chunks of the Earth into space. One crashed back down, but it gave a boost to the other chunk, leaving it in orbit to become the Moon.

Here is an idea that likely never crossed the mind of most space enthusiasts – a gas emitted from broccoli (and other plants) is one of the most indicative signs of the existence of life on a planet. At least according to a new study from researchers at the University of California Riverside.

That gas, methyl bromide, has long been associated with life on Earth. It occurs naturally from the process of plants defending themselves. Methylation, as the defense process is known, allows plants to expel foreign contaminants, such as bromide, by attaching a series of carbon and hydrogen atoms to it, thereby gasifying it and allowing it to escape into the air.

Methyl bromide, in particular, is interesting from an astrobiological perspective. It was used as a pesticide until the early 2000s and has several important advantages over other potential biosignatures if it shows up in an exoplanet’s atmosphere.

First, it has a relatively short lifespan in a planet’s atmosphere. This is particularly important for exoplanet searches, as it means whatever process produces the gas is most likely still active. Its presence isn’t simply a result of a geological event that happened eons ago.

A second advantage is one that all astrobiologists love to see – there are very few non-biological processes that produce the gas, and even those processes aren’t typically natural. Despite now being considered a hazardous chemical, methyl bromide was produced in large quantities for use as a pesticide before being regulated due to its deleterious health effects.

How would Earth appear to alien astronomers? What would their observations tell them about Earth if they were searching the heavens for signs of habitability like we are? It’s a fun thought experiment.

But the experiment is more than just fun: it’s scientifically instructive. In many ways, it’s easier to study our planet and how it appears and then extrapolate those results as far as they go.

A new study shows that finding evidence of life on Earth may depend on the season alien astronomers are observing.

Almost nothing in space science generates as much widespread excitement as finding a potentially habitable planet. The headlines spread like a virus through the internet with only minor mutations from site to site. So far, we’ve only got glimpses and hints of exoplanets that might be able to support life. We’ve got a long way to go.

It’ll take a lot of science and innovative reasoning before we ever get to a point where we can say “Yes. This distant planet is habitable.” A new study might be part of getting to that point by examining Earth’s outward appearance through different seasons.