Astronomers discovered something strange about 'potentially hazardous' asteroid Phaethon

Space.com ^ | By Stefanie Waldek p

[BenLurkin]

The Japan Aerospace Exploration Agency intends to launch its DESTINY+ mission to the near-Earth asteroid Phaethon in 2024, with the aim of flying by the space rock in 2028, so this "potentially hazardous" asteroid has been studied intensely in the lead-up to the mission.

Researchers recently made one particularly notable discovery about Phaethon: Its spin is speeding up. The asteroid's rotational period is decreasing by 4 milliseconds per year. Even a small change like this could impact the DESTINY+ observations. Knowing the specific spin rate allows the team to more accurately predict the asteroid's orientation during the spacecraft's flyby — in turn, that allows the team to be more specific with their observations.

It's rare for an asteroid's spin to change; Phaethon is just the 11th known asteroid to show a change in its rotational period, and it's the largest of those space rocks, with an average diameter of 3.4 miles (5.4 kilometers).

Using data and observations from 1989 through 2021, Sean Marshall, a planetary scientist at Arecibo Observatory in Puerto Rico, created a model to determine the shape of Phaethon in preparation for the DESTINY+ mission.

"The predictions from the shape model did not match the data," Marshall said in a statement. "The times when the model was brightest were clearly out of sync with the times when Phaethon was actually observed to be brightest. I realized this could be explained by Phaethon's rotation period changing slightly at some time before the 2021 observations, perhaps from comet-like activity when it was near perihelion [the point in its orbit nearest to the sun] in December 2020."

Marshall determined that the model that best fit the data included constant rotational acceleration — in other words, the regular decrease of Phaethon's rotational period of 4 milliseconds per year.

[rellic]

“I kinda wonder why Arecibo hasn’t been replaced by giant phased arrays in some remote locations.”
it is called SMT in Hawaii.
The Chinese built a brand new “Arecibo” in China so why copy it? They write papers just like every one else.
Astronomy covers a wide spectrum of energy, to study an object of interest.
It often takes several Observatories, all with vastly different capabilities to make a discovery.
A team effort if you will.

Time will tell.
I still would rather cure most cancers than
read papers about 13 billion year old stars,
that we only just discovered.
The stars are probably long gone by now.

In perspective the Photons warming your body, took 8 minutes or so to get here from our Suns surface.
Those Photons are probably about a million years old, they started as Gamma rays in the Fusion reactions deep inside the sun.
Think about that a bit.

[Tunehead54]

"I bet if a 3.4 mile diameter asteroid hit Washington D.C., the impact would be heard in Denver... Chandeliers rocking in Las Vegas."

---

So, except for the chandeliers jingling in Las Vegas - no real downside?

;-)

[no-s]

> rotational period is decreasing by 4 milliseconds per year.

spinning up. my bad. yes, perhaps shrinking. Which could be gravitational consolidation, I guess...