NASA's Voyager 2 becomes second spacecraft to reach interstellar space
Washington: More than four decades after beginning its epic journey, NASA's Voyager 2 spacecraft has crossed the elusive boundary that marks the edge of the Sun's realm and the start of interstellar space, scientists have announced.
According to the researchers at the University of Iowa in the US, Voyager 2 has entered the interstellar medium (ISM), the region of space outside the bubble-shaped boundary produced by wind streaming outward from the Sun.
This makes Voyager 2 the second human-made object to journey out of the Sun's influence, following the US space agency's Voyager 1's solar exit in 2012.
The study, published in the journal Nature Astronomy, confirmed Voyager 2's passage on November 5, 2018, into the ISM by noting a definitive jump in plasma density detected by a plasma wave instrument on the spacecraft.
The marked increase in plasma density is evidence of Voyager 2 journeying from the hot, lower-density plasma characteristic of the solar wind to the cool, higher-density plasma of interstellar space, the researchers said.
It is also similar to the plasma density jump experienced by Voyager 1 when it crossed into interstellar space, they said.
"In a historical sense, the old idea that the solar wind will just be gradually whittled away as you go further into interstellar space is simply not true," said Professor Don Gurnett from the University of Iowa, and corresponding author on the study.
"We show with Voyager 2 -- and previously with Voyager 1 -- that there's a distinct boundary out there. It's just astonishing how fluids, including plasmas, form boundaries," Gurnett said.
Voyager 2's entry into the ISM occurred at 119.7 astronomical units (AU), or more than 11 billion miles from the Sun. Voyager 1 passed into the ISM at 122.6 AU.
The spacecraft were launched within weeks of each other by NASA in 1977, with different mission goals and trajectories through space. Yet they crossed into the ISM at basically the same distances from the Sun.
That gives valuable clues to the structure of the heliosphere -- the bubble, shaped much like a wind sock, created by the Sun's wind as it extends to the boundary of the solar system, the researchers said.
"It implies that the heliosphere is symmetric, at least at the two points where the Voyager spacecraft crossed," said Bill Kurth, University of Iowa research scientist and a co-author on the study.
"That says that these two points on the surface are almost at the same distance," Kurth said. "There's almost a spherical front to this. It's like a blunt bullet," Gurnett added.
Data from the instrument on Voyager 2 also gives additional clues to the thickness of the heliosheath, the outer region of the heliosphere and the point where the solar wind piles up against the approaching wind in interstellar space, which Gurnett likens to the effect of a snowplow on a city street.
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India-bound LPG tanker clears Hormuz
New Delhi (PTI): A tanker carrying liquefied petroleum gas (LPG) for India has sailed out of the Strait of Hormuz and is now headed towards the country, an official statement said on Sunday.
The Marshall Islands-flagged LPG carrier MT Sarv Shakti, loaded with 46,313 tonnes of LPG and staffed by 20 crew, including 18 Indians, cleared the key shipping chokepoint on May 2 and is expected to reach Visakhapatnam on May 13, it said.
The cargo -- enough to meet half a days requirement of the country -- will partly tide over supply constraints being faced since the start of the West Asia conflict more than two months back.
Ship-tracking data showed its position in Oman Gulf on Sunday evening.
The very large gas carrier has previously made runs between the Persian Gulf and Indian ports, has been chartered by state-owned Indian Oil Corporation (IOC).
Sarv Shakti is the first India-linked tanker to cross the war zone since a weeks-old US blockade of ships tied to Iran began, pushing transits through Hormuz back down to almost zero.
There are as many as 14 Indian flagged or India-owned vessels still stranded on the west side of the Strait of Hormuz.
The statement said no incident involving Indian-flagged vessels has been reported in the past 24 hours. The Ministry of Ports, Shipping and Waterways is working closely with the Ministry of External Affairs, Indian missions and maritime stakeholders to ensure crew welfare and uninterrupted operations.
The Directorate General of Shipping (DG Shipping) control room has handled 8,373 calls and more than 17,965 emails since activation, including 38 calls and 127 emails in the last 24 hours.
India has also facilitated the repatriation of more than 2,953 seafarers so far, including 31 in the past day from across the Gulf region.
Port operations across the country remain normal with no congestion reported, the statement added.
