Minneapolis is likely to be asked to help share the operating costs of a new planetarium built atop the downtown library.

A task force advising the Hennepin County Board agreed Monday that it needs to know the city's stance on sharing the planetarium's subsidy before it makes decisions about where to put it.

Commissioners serving on the task force agreed to ask the County Board to make such a request to the city. The projected subsidy ranges between $563,000 and $622,000 in the first five years of operation.

The city is willing to explore if it could scrape together a part of that, said Council Member Scott Benson, a task force member.

"Obviously, we're cash-strapped," he said. "It would be a tough thing for us to find a source."

The consensus to ask the city how much it would pony up comes as the task force is trying to decide among several options: sticking with the original plan to build atop the library, building it on an adjacent block, building it elsewhere downtown, or even putting it in the suburbs. There seems to be the greatest support for a library-top facility, since the city spent an extra $1.8 million to prepare the library structure for the addition of a planetarium.

Part of the uncertainty on the planetarium issue comes from the county inheriting what had been a city-led planetarium project when the county took over city libraries last January. The project came with $22 million in state bonding for a library planetarium, which has an estimated cost of $39 million.

But county Library Director Amy Ryan has reservations about the rooftop planetarium because of the effect of construction on the library. The task force also has discussed the possibility of building the planetarium one block north of the library, but switching sites might require the Legislature to reauthorize the bonding.

One task force member, Commissioner Mark Stenglein, said he has been approached by developer Robert Lux about the possibility of putting the planetarium at Lux's pending development at 11th Street and Hennepin Avenue S. Lux confirmed that he is interested in some sort of regional draw for the development.

But Commissioner Gail Dorfman, the task force chair, said she thinks that there would be synergies between a joint library and planetarium because both appeal to children and they could share some operating costs.

Around the nation, planetaria typically require operating subsidies, which are usually obtained from government. Those typically provide about 25 percent of a facility's income, according to planetarium boosters.

Steve Brandt • 612-673-4438