July 15, 21:52

Solar System Object Previously Considered Asteroid Classified as Rare 'Dark Comet'

The object that astronomers have been observing since 1998 surprised the scientific community by demonstrating signs of cometary activity. Initially classified as an asteroid, 1998 SH2 has been identified as a rare 'dark comet.'

Trajectory Change and Mystery

The study showed that some bodies in the Solar System can conceal hard-to-detect characteristics. Typically, comets reveal their presence through a coma and tails formed when sunlight heats the ice on the surface. Gas emission can also act as a small impulse, altering orbits.

A study published in Nature Astronomy analyzed 1998 SH2, which was observed for nearly three decades. In August 2025, as it approached Earth, the object was in a position different from what models based solely on gravity predicted. At the end of the same month, the Vikrota Observatory, part of the Southern Observatory for Near-Earth Asteroid Studies Wykrota-Centro de Estudos Astronômicos de Minas Gerais, located in Serra da Piedade, re-detected the body.

Calculations showed that the object was 19 standard deviations away from its expected position. For scientists, this discrepancy indicated additional acceleration, likely caused by gas ejection.

Visual Evidence of Hidden Comet

After detecting the trajectory change, the team studied deep images obtained by telescopes in Chile and Hawaii. These recordings captured a faint coma and a narrow tail over 20 arcseconds long. This was the first direct confirmation of cometary activity predicted based on this type of orbital change.

According to the study, dust ejection occurred continuously from late August to September 2025, indicating a process of sublimation—the transition of ice directly from a solid to a gaseous state. Key findings include: 1998 SH2 was previously classified as an asteroid; the body demonstrated acceleration unexplained by gravity; images confirmed the presence of a coma and tail; and this research may help in identifying other dark comets.

Significance for Planetary Defense

Scientists emphasize that 1998 SH2 does not pose an impact threat to Earth in the near future. Nevertheless, the existence of such objects could influence calculations in the field of planetary defense. Identifying these bodies is also important because an object considered an asteroid might possess cometary characteristics, changing assessments of its composition and potential deflection strategies.

Furthermore, the research suggests that an ancient population of dark comets may have contributed to the delivery of water to Earth during the planet's formation. The work published in Nature Astronomy expands knowledge about small bodies in the Solar System and shows that long-term observations can yield unexpected discoveries.

olhardigital.com.brJuly 4, 16:30

NASA detects high-speed object resembling a surfboard around the Moon

In 2009, NASA began detailed investigation of the lunar surface with the launch of the Lunar Reconnaissance Orbiter (LRO). The LRO mission aimed to identify potential landing sites, natural resources, and notable features, such as lava tubes. Currently, the spacecraft has mapped a large part of the lunar surface, excluding the polar areas which remain deeply shadowed.

Detection of Danuri in 2024

In 2024, the LRO captured images of an object resembling a 'surfboard' moving rapidly around the celestial body's orbit. This object is the Danuri spacecraft, which was launched by South Korea in August 2022. It is the country's first lunar orbiter, whose mission includes developing and testing technologies, such as space internet, in addition to creating a topographic map of the lunar surface.

Objectives of the Korean Mission

According to the Korea Aerospace Research Institute (KARI), responsible for the mission, the work performed by the Danuri satellite will assist in selecting future landing sites and identifying valuable resources, such as uranium, helium-3, silicon, aluminum, and water ice.

Instruments and Technological Collaboration

The South Korean orbiter is equipped with various instruments, including a spectrometer, a magnetometer, and several cameras. One of these cameras, called Shadowcam, has the capability to photograph the obscured polar regions that the LRO cannot map. It is relevant to note that this specific instrument for capturing dark areas at the lunar poles was developed by NASA.

Detailed Orbital Encounters

In March 2024, the two orbiters crossed trajectories at a combined speed of 11,500 km/h. Three distinct orbits were observed, allowing the LRO to record Danuri in accelerated motion. The vertical distance between the two vehicles varied during each pass. In the first image, the LRO was five kilometers above the Korean spacecraft, requiring the NASA orbiter to adjust its aiming angle to 43 degrees below standard. In the second orbit, the separation was smaller, only four kilometers. In the third and final orbit, the distance was eight kilometers, at which point the LRO was directed at a 60-degree angle.

Mutual Recording in Orbit

This was not the first visual recording between the two bodies in lunar orbit. In April 2023, using the ShadowCam, it was Danuri that captured the LRO, when it was 18 kilometers above the American satellite.